1. Field of the Invention
The present invention relates to a telecommunication system, and more particularly, to a femtocell wireless signaling/data mesh network for multi-user, multi-mode baseband signaling methods, timing/frequency synchronization, and receiver architectures.
2. Description of the Prior Art
In general, conventional basestation transceivers are connected to the basestation controllers through dedicated communication links such as T1 or E1 lines. These basestation controllers are connected to each other and also connected to other network equipments such as Serving GPRS Support Node (SGSN) or Gateway GPRS Support Node (GGSN) in General Packet Radio Service (GPRS) network.
For example, in a 3G Universal Mobile Telecommunications System (UMTS) system, each of basestation controllers (RNC) is connected to a plurality of basestation transceiver (Node B) to form a communication network called UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is connected to the Core Network equipments such as SGSN, GGSN, MSC (Mobile Switching Center), CGF (Charging Gateway Function), HLR/VLR (Home Location Register/Visitor Location Register), and/or MGW (Media Gateway) using Asynchronous Transfer Mode (ATM) switches over either T1 or E1 lines.
Recently, a femtocell (Home Node B) is a miniature device in the size of a CPE which functions as a combination of RNC and Node B and is connected through internet to the Core Network. Please refer to FIG. 1. FIG. 1 illustrates comparisons between a conventional cellular network architecture and a femtocell network architecture. As shown in FIG. 1, the cellular network architecture 1 is shown on the left-hand side and the femtocell network architecture 2 is shown on the right-hand side. In the cellular network architecture 1, the communications between the RNCs 10 and 12 are possible; in the femtocell network architecture 2, the communications between femtocells 20 and 21 must router through a concentrator/aggregator 22. Therefore, the traffic loading between the concentrator/aggregator 22 and femtocells 20 and 21 will become very heavy.
It should be noticed that since RNC and Home Node B are now combined into the femtocell while femtocells are connected to the Core Network through Internet using TCP/IP protocol, the femtocell network architecture 2 can eliminate the need for any dedicated connections between RNC and Home Node B. Please refer to FIG. 2. FIG. 2 illustrates an example of no communication/connections between femtocells available in the 3G UMTS system. Since there are no direct communication/connections between femtocells 240-242, 250-252, and 260-262 available in the 3G UMTS system 23 as shown in FIG. 2, all communications in the 3G UMTS system 23 must go through the packet data network/internet 230 or any intermediate devices such as a femtocell concentrator/aggregator 2340. That is to say, the femtocell concentrator/aggregator 2340 is used as a gateway for femtocells wanting to connect to the telephone/DSL network 233. In the conventional UTRAN, protocol interfaces are defined to facilitate the communications between Node B and RNC, RNC and RNC, RNC and Core Network components. There is no communication protocols defined between Node Bs. Therefore, the traffic loading between femtocells and concentrators (aggregator) will become heavier, the cost of the network equipment will become higher, and handovers among basestations will also become slower.
Moreover, when a wireless link is used for signaling and data transmissions between the femtocells, there are still many challenges needed to be overcome as follows. (1) Femtocell must be able to maintain a list of neighboring cells information; (2) Femtocells must be able to self-define the roles they play for a given link, such roles include SRNC, DRNC, and CRNC, but not limited to these cases; (3) Wireless link must be able to establish a reliable link to the neighboring femtocells; (4) Femtocells must be able to exchange physical layer information through the wireless link, such as primary scrambling code, RF capability (e.g., frequency channel supported, maximum/minimum power, average power), or current cell loading; (5) Femtocell must be able to route the information received through Wi-Fi links to its RRM entity for further processing; (6) Femtocell must be able to detect the RF interference level at each Wi-Fi frequencies and negotiate with the neighboring femtocells to switch to the best channel it perceives; (7) The Wi-Fi module inside the Femtocell must be able to perform in both the infrastructure mode and the ad hoc mode; (8) Femtocell must be able to share L1 measurement information between neighboring cells.
Therefore, the invention provides a femtocell wireless signaling/data mesh network to solve the aforementioned problems.